This invention relates to method and apparatus for testing the sealing effectiveness of a radial-lip type of oil seal.
Since radial-lip oil seals are precision products made in large quantities it is on the one hand very desirable and on the other hand very difficult to determine whether they are effective before they are installed, usually in some part of an automobile or machine which is completely inaccessible without considerable removal of parts. Oil seals can, of course, be tested by placing them on a shaft similar to that on which they are to be used and actually running them under conditions to which they are to be subjected and noting whether there is leakage of oil. However, this very slow test is quite impractical except on a small sampling of seals. It is very useful in determining the practicality of a particular design, but is not applicable for testing a large number of seals as actually produced.
As a result, there have been proposals for testing seals in a more rapid manner. The apparatus disclosed in the Dega U.S. Pat. No. 3,097,521 tests for leakage by using air under such pressure that there is bound to be leakage, the amount of leakage then being determined. The test results do not completely correspond with the results of actual use of the seals and do not, in fact, determine with sufficient accuracy which seals are likely to leak under actual conditions of use. This failing is due to the fact that the test bears small relation to the actual conditions of use, where such pressures as are used in testing are not encountered.
Static air test methods have likewise been proposed where the air pressure is such that there is no leakage except in defective seals. However, it has been determined that in many instances seals which will hold air pressure under static conditions will not prevent oil leakage during actual use.
Thus, it is an object of the present invention to provide both method and apparatus for testing a seal in a rapid manner so that a large number of seals, possibly even the entire production run, can be tested in lieu of mere visual inspection, and also, to enable the test results to correspond more nearly with the actual performance to be expected from such seals.